Correction to This Article
This article incorrectly described Sen. Mitch McConnell (R-Ky.) as speaking "in favor" of U.S. military involvement to ground the air forces of Libyan leader Moammar Gaddafi. As the story noted, the Senate minority leader told an interviewer that he thinks a Western-imposed no-fly zone is "worth considering." McConnell also said that the United States should find ways to be helpful that are "certainly short of sending in our own military personnel."

Congressional leaders prodded the Obama administration on Sunday for a more aggressive U.S. response to Libya's increasingly brutal attacks on opposition groups - calling for a no-fly zone and other military measures - but White House officials cautioned against being drawn into a potentially protracted and costly military campaign.

Sen. John F. Kerry (D-Mass.), chairman of the Foreign Relations Committee, for the first time raised the possibility of bombing military airfields in Libya to deny the use of runways to Moammar Gaddafi's air force. Two of the Senate's top Republicans, Mitch McConnell (Ky.) and John McCain (Ariz.), also spoke in favor of U.S. military involvement to keep Libyan warplanes grounded.

"We can't risk allowing Gaddafi to massacre people from the air," McCain, the ranking Republican on the Armed Services Committee, said on ABC's "This Week With Christiane Amanpour."

But White House officials appeared to play down expectations of an expanded U.S. military role in the immediate future. While insisting that no options have been ruled out, White House Chief of Staff William M. Daley cited the difficulty of enforcing a no-fly zone over Libya, a vast country armed with modern, Russian-supplied antiaircraft defenses.

"Lots of people throw around phrases like no-fly zone," Daley said on NBC's "Meet the Press." "They talk about it as though it's just a video game."

Daley's remarks echoed the caution voiced by Defense Secretary Robert M. Gates, who dismissed as "loose talk" the clamor for a U.S.-led air campaign. Gates said that any effort to secure the skies over Libya, a country roughly the size of Alaska, would have to begin with military strikes on Gaddafi's air defense network and would inevitably lead to an expanded U.S. mission.

Kerry and other senators argued Sunday that Libya's air force could be disabled without the kind of expense and commitment required to maintain previous no-fly zones in Iraq and the Balkans. The Massachusetts Democrat also called for turning over to rebel groups some of Gaddafi's estimated $30 billion in frozen assets.

A no-fly zone is "not the only option for what one could do," Kerry said.

"One could crater the airports and the runways and leave them incapable of using them for a period of time," he said on the CBS news program "Face the Nation." McConnell, on the same program, said a no-fly zone was "worth considering."

The debate over U.S. options highlights the dilemma facing the Obama administration as Libya veers closer to all-out civil war. The White House is confronting a range of options, including increased humanitarian aid and different gradations of military intervention, although none is likely to end the violence immediately, administration officials concede.

Nor is the United States likely to gather enough international support in the short term to quickly push Gaddafi from power, the sources said. Russia and China, permanent members of the U.N. Security Council, have objected to any military action authorized by the United Nations, as has Brazil. The Arab League has also spoken out against any Western-backed military intervention and raised the possibility of imposing a no-fly zone in coordination with the nations of the African Union.

Senior Obama administration officials say days of fighting - along the east-west coastal road to Tripoli and in and around the Libyan capital itself - has resulted in a strategic deadlock on the ground. The administration is not ready yet, though, to call the situation a civil war.